President Thein Sein’s government has routinely denied the existence of political prisoners, saying all people sentenced to jail have been convicted legitimately of breaking the nation’s laws. Nevertheless, hundreds of prominent political detainees have been freed since the former general took office two years ago after an army junta was dissolved.

In February, Thein Sein appointed a 16-member committee to review the cases of inmates identified by opposition groups as prisoners of conscience. Some cases are complicated because they involve bombings or threats to state security or national stability. Rights groups say many other people were wrongfully convicted and given extreme sentences for actions that would not be considered crimes elsewhere.

Ye Aung, a former prisoner and a member of the government committee, said at least 59 political prisoners were released Tuesday and that at least 300 others remain incarcerated, most of them members of ethnic minorities.

Opposition leaders and rights groups have accused the government of using political prisoners as ‘‘bargaining chips’’ — releasing some to prove progress, holding others to push the West to ease more sanctions.